A three thread overedge stitch is formed on the edge of the material, preventing the material from unravelling. Also when used on two plies of material it holds the plies together near their edges. The elements required to form a three thread overedge stitch include the needle, the upper looper, and the lower looper. These elements cooperate in a predetermined manner to form the stitch. In their paths of movement, they all pass extremely close to one another.
Many of today's industrial sewing machines are operated at extremely high speeds, up to 8000 stitches per minute. At these high speeds many sewing problems occur, such as non-uniform stitches, skipped stitches, and thread breakage. These same problems are also encountered when sewing heavy weight material. As a result, adjustment of the needle and the upper and lower loopers in relation to each other becomes very critical at these high speeds and when sewing extremely heavy weight materials.